Racing thoughts at bedtime are usually not caused by a single “overactive brain region”; they reflect an interaction between internally directed thinking, arousal, attention, and the brain’s transition from wakefulness to sleep. The default mode network (DMN) is involved, but describing bedtime rumination simply as “DMN hyperactivity” is an oversimplification. (PubMed)
Try this for 60 seconds
Lie comfortably and breathe at roughly 5–6 breaths per minute: inhale gently for about 4–5 seconds, then exhale for about 5–6 seconds. Keep the breath quiet and comfortable rather than taking unusually deep breaths.
Slow breathing can shift autonomic activity toward greater parasympathetic influence and may reduce physiological arousal. A 2026 systematic review found improvements in self-reported sleep quality and duration with slow breathing before bed, although objective sleep findings remain inconclusive. (PubMed)
The goal isn’t to force your thoughts to stop. It is to make the body’s transition toward sleep easier.
What is actually happening in the brain?
Default mode network: the brain’s internal storyteller
The default mode network (DMN) is a collection of interacting brain regions involved in internally directed processes such as autobiographical memory, self-referential thinking, imagining, and spontaneous thought. (PubMed)
When external stimulation decreases at night, there is more opportunity for internally generated thoughts to become noticeable:
- replaying conversations
- planning tomorrow
- remembering something from years ago
- imagining future situations
- worrying about unresolved problems
This doesn’t mean the DMN is malfunctioning. Internal thought is a normal brain function.
The problem can arise when internal thinking remains highly engaging while the rest of the sleep system is trying to reduce alertness.
Hyperarousal: the other half of the picture
Hyperarousal means that physiological and cognitive alertness remain elevated when sleep would normally be taking over.
This can involve several systems, including autonomic arousal, attention, emotional processing and interactions between the DMN, salience network and executive-control networks. Neuroimaging studies of insomnia have found altered connectivity across several of these networks rather than one consistent abnormality in the DMN alone. (PubMed)
That’s why trying to “switch off the DMN” is probably the wrong target.
A better goal is to reduce the conditions that keep internally generated thoughts emotionally or cognitively activating.
Why thoughts become louder in bed
During the day, attention is continually captured by external tasks, conversations, movement and sensory information.
At night, those distractions disappear.
If unresolved concerns are still important to you, the quieter environment can give them more cognitive space. Research also shows that disturbed sleep and sleep deprivation are associated with more disruptive forms of spontaneous thought and mind-wandering. (PubMed)
There can also be a feedback loop:
Thought → arousal → greater awareness → more concern about sleep → more thought
For example, noticing “I’m still awake” can turn ordinary mental activity into a performance problem: “I need to fall asleep now.”
That additional monitoring can itself maintain alertness.
Well-established vs. plausible vs. uncertain
Well-established: The DMN contributes to internally generated thought, including self-related thinking and mind-wandering. Insomnia is also associated with altered activity or connectivity involving the DMN and several other brain networks. (PubMed)
Plausible: For some people, excessive pre-sleep rumination may contribute to difficulty transitioning into sleep, partly through interactions between internally directed cognition and physiological arousal. Studies have found relationships between pre-sleep DMN connectivity and subsequent sleep, but this does not establish that DMN activity is the primary cause. (PubMed Central (PMC))
Uncertain: There is no established brain-based formula such as “racing thoughts = excessive DMN activity.” Recent research finds both increased and decreased connectivity in different brain regions and networks among people with insomnia. Because many studies are cross-sectional, these findings cannot establish whether altered connectivity causes insomnia or results from it. (PubMed)
How to make racing thoughts less activating
Rather than attempting to suppress thoughts directly, use strategies that reduce their salience and physiological activation.
1. Slow the body first
Use comfortable slow breathing for a minute or two. The evidence supports effects on autonomic regulation, although it does not prove that slow breathing specifically “turns off” the DMN. (PubMed)
2. Stop solving problems in bed
If your brain starts planning tomorrow, don’t turn the bed into a planning desk.
Before bed, write down the few things that genuinely need attention tomorrow. The objective isn’t to empty your mind; it’s to give your brain somewhere else to store unfinished tasks.
3. Don’t monitor sleep excessively
Checking the clock repeatedly can transform ordinary wakefulness into a source of threat or urgency.
If you aren’t sleepy, forcing sleep can become counterproductive. Evidence-based insomnia treatment uses behavioral strategies specifically designed to weaken the association between the bed and prolonged wakefulness.
Common mistakes
- Trying aggressively to stop thinking. Suppression can make the unwanted thought more noticeable.
- Checking the time repeatedly. This can increase pressure about how much sleep remains.
- Using stimulating content as a distraction. Scrolling, emotionally intense videos or work may occupy attention while keeping the brain engaged.
A simple evening sequence
You don’t need a complicated “brain-hacking” routine.
About 1 hour before bed: reduce demanding work and emotionally stimulating activities.
Before getting into bed: briefly write down unresolved tasks or tomorrow’s priorities.
In bed: use comfortable slow breathing and allow thoughts to arise without following every one.
If a thought appears, you can notice it without completing the entire mental storyline. The objective is less engagement, not a completely blank mind.
What this doesn’t mean
Racing thoughts do not automatically mean that your DMN is abnormally active.
They also don’t mean that you have insomnia, anxiety, or another disorder based on this symptom alone.
And you don’t need to eliminate the DMN to sleep. The network has important normal functions involving memory, self-reflection and internally generated thought. (PubMed)
The scientifically safer interpretation is that difficulty falling asleep can involve interacting cognitive and physiological systems, with DMN-related processes being one part of that larger network.
If difficulty falling or staying asleep becomes persistent and significantly affects daytime functioning, a clinician or sleep professional can help determine whether chronic insomnia or another sleep problem is involved.
Bottom line
Racing thoughts in bed are better understood as a state of persistent internal cognitive activity interacting with arousal—not simply as “DMN hyperactivity.” You cannot reliably switch off one brain network on command. A more useful strategy is to reduce physiological activation, stop treating wakefulness as an emergency, and give unfinished thoughts less opportunity to become extended problem-solving sessions.
The immediate experiment is simple: slow, comfortable breathing for 60 seconds, without trying to force your mind to become blank.